1. Field of the Invention
The present invention relates to an image reading apparatus for reading an image recorded on a photographic film or the like and, more particularly, to an image reading apparatus such as a photographic printer and a film scanner whose light source portion is improved.
2. Description of the Related Art
In the conventional photographic printer, the light is irradiated from a light source such as a halogen lamp and LED elements to a film image such as negative film. Then, the light that is transmitted through or was reflected by the film image is read out by an image reading means such as a CCD sensor or the like.
When LED elements are used as the light source, a structure is available where a plurality of red light emitting (R) LEDs, green light emitting (G) LEDs and blue light emitting (B) LEDs are arranged in a matrix shape, and each of the LEDs is individually controlled in terms of light emitting luminance and light emitting time, so that light spectrum distribution (three-color light components) and light amount of the printing light for the film image can be varied. In this case, a power source having a large capacity such as a power source when a halogen lamp is used as a light source is not necessary, so that the structure can be simplified and compact.
Moreover, there is available the image reading apparatus which detects a scratch or foreign matter on the film image in such a manner that non-visible light such as infrared light (IR) is irradiated to the film and the light transmitted through the film or reflected by the film is read out by the reading means.
However, the light amount necessary for reading out the film image such as a negative film differs for each color of blue(B), green (G), red (R) and the infrared light depending on the orange colored mask density (that is, the base density of the color negative film) and the spectral transmittance (or spectral reflectance) of an overly exposed negative film.
Thus, according to the technology disclosed in Japanese Patent Application Laid-Open No. 8-22081, the light emitting luminance, light emitting time and the number of elements to be driven are controlled in combination thereof so as to vary the light spectrum distribution and light emitting amount. Namely, the reading is carried out such that the light emitting luminance of each LED element is varied by changing the value of the current to be supplied to the LED element, or the light amount emitted from each LED element is varied by controlling the input current supplying time for the LED element.
However, a problem arises where the controlling operation such as for a control timing becomes complicated since the current value to be inputted to each LED element and its energizing time must be controlled individually for each color in accordance with the light amount required for each of R, G, B and IR.
The number of LED elements emitting light of a color which requires a larger light amount for reading and the number of LED elements emitting light of a color which requires a smaller light amount for reading, are the same. Thus, the LED elements are not arranged efficiently.
In order to achieve the above described object, a first aspect of the present invention is an image reading apparatus comprising a light source having a plurality of LED elements composed of red (R) light emitting elements (R-LEDs), green (G) light emitting elements (G-LEDs) and blue (B) light emitting elements (B-LEDs) which are arranged in a matrix form and which emit independently or simultaneously red (R) light, green (G) light and blue (B) light by a predetermined current being supplied thereto; and a photoelectric converting element for reading lights transmitted through or reflected by an original irradiated with the lights emitted from the light source, wherein the numbers of the R-LED elements, the G-LED elements and the B-LED elements arranged in the matrix are r, g and b, respectively, and r less than g less than b, and the R-LED elements the G-LED elements and the B-LED elements are uniformly distributed in the matrix, respectively.
The optical transmittance of a photosensitive material such as a color negative film varies in accordance with the wavelength region. The spectral transmittance of a color negative film at each wavelength region is generally B less than G less than R, i.e., the transmittance of B light is the lowest, the transmittance of R light is the highest, and the transmittance of G light falls between the two. Further, in addition to this variation in the transmittance, the spectral transmittance of a color negative film at each wavelength region varies with conditions, such as under-exposed, normal-exposed and over-exposed conditions, of the color negative film which has been exposed and processed, so that the light amount transmitted through the color negative film and incident upon the photoelectric converting element is changed. Accordingly, when a color negative film (original) on which an image has been recorded is irradiated with light emitted from the light source, the light amount required for reading the image which is incident upon the light receiving surface of the photoelectric converting element varies in accordance with the wavelength regions. Therefore, in order to read an image, less R light is required, more G light is required, and even more B light is required. According to the first aspect of the present invention, when the red (R) light emitting elements (R-LEDs), the green (G) light emitting elements (G-LEDs) and the blue (B) light emitting elements (G-LEDs) are arranged in a matrix form in a light source, the numbers of R-LED elements, G-LED elements and B-LED elements are r, g and b, respectively, and r less than g less than b, so that the light amount required for image reading which varies with the wavelength regions can be ensured. Further, the R-LED elements , the G-LED elements and the B-LED elements are uniformly distributed in the matrix, respectively. A predetermined current, preferably substantially the same current, can be supplied to the light emitting elements of the respective colors and a light amount required for image reading which varies with the wavelength regions can be ensured without inputting current of the different values to each color of light emitting LED elements. Therefore, the light amount required for image reading can be ensured simply and effectively.
A second aspect of the present invention is to provide an image reading apparatus comprising: light source having a plurality of LED elements composed of red (R) light emitting elements (R-LEDs), green (G) light emitting elements (G-LEDs), blue (B) light emitting elements (B-LEDs) and infra-red (IR) light emitting elements (IR-LEDs) which are arranged in a matrix form and which emit independently or simultaneously red (R) light, green (G) light, blue (B) light and infra-red (IR) light by a predetermined current being supplied thereto; and a photoelectric converting element for reading lights transmitted through or reflected by an original irradiated with the lights emitted from the light source, wherein the numbers of the R-LED elements, the G-LED elements, the B-LED elements and the IR-LED elements arranged in the matrix are r, g, b and ir, respectively, and ir less than r less than g less than b, and the IR-LED elements, the R-LED elements, the G-LED elements and the B-LED elements are uniformly distributed in the matrix, respectively.
In the present invention, when three types of LED elements emitting red, green and blue lights are used, the ratio of numbers r:g:b of the LED elements in the matrix are preferably in the range of 1:1.5-3:2-6, and more preferably 1:2:4.
In the present invention, when four types of LED elements emitting red, green, blue and infra-red lights are used, the ratio ir:r:g:b of the numbers of the LED elements in the matrix are preferably in the range of 0.2-0.9 1:1.5-3:2-6, and more preferably 0.5:1:2:4.
In the above structural arrangement, when the number ratio of r:g of the LED elements is 1:2-3, b is necessarily larger than g.
As described above, when a color negative film (original) is irradiated with light emitted from the light source, the light amount which is incident upon the light receiving surface of the photoelectric converting element and which is necessary for reading an image varies in accordance with the light wavelength regions. The amount of light necessary for reading an image increases in the order of R (least), G and B (greatest). Further, a negative film is irradiated with non-visible light such as infra-red light and the light transmitted through or reflected from the negative film is read by a reading means such as a CCD sensor so that scratches or foreign matter on the film can be detected. In this case, as the spectral transmittance in the infra-red region is higher than that of the visible region, the infra-red light amount incident upon the light receiving surface of the photoelectric converting element, which light amount is necessary for measurement, can be ensured, even if the amount of infra-red light emitted from the light source is smaller than the amount of visible light emitted from the light source. When image reading is carried out by irradiating a color negative film with visible light, the amounts of the red (R), green (G) and blue (B) lights incident upon the light receiving surface of the photoelectric converting element decrease in the order of R (greatest), G and B (least). In addition, when a color negative film is irradiated with infra-red light and the presence of scratches or foreign matter on the color negative film is detected by the light transmitted therethrough, the amount of infra-red light incident upon the light receiving surface of the photoelectric converting element can be smaller than the amount of the red light. Namely, when the infra-red (IR) light emitting elements (IR-LEDs), the red (R) light emitting elements (R-LEDs), the green (G) light emitting elements (G-LEDs) and the blue (B) light emitting elements (G-LEDs) are arranged in a matrix form in a light source, the numbers of IR-LED elements, R-LED elements, G-LED elements and B-LED elements are ir, r, g and b, respectively, and ir less than r less than g less than b, so that a light amount required for image reading which varies in accordance with the wavelength region can be ensured. Further, the IR-LED elements, the R-LED elements , the G-LED elements and the B-LED elements are uniformly distributed in the matrix, respectively. A predetermined current, preferably substantially the same current, can be supplied to the color light emitting elements of each color, and a light amount required for the image reading which varies in accordance with the wavelength regions can be ensured without inputting different current to the light emitting LED elements of each color. Therefore, the light amount required for the image reading can be assured simply and effectively.
In the present invention, the original whose image to be read is preferably a color negative film having an orange colored mask.
In the present invention, a light guiding member for making the light emitted from the light source into diffuse light is disposed between the light source and the original. The light guiding member comprises a block having a substantially transparent trapezoidal configuration as seen in view and a refractive index of from 1.2 to 1.9, and a light diffusing plate.
Further, the photoelectric converting element is a monochromatic type CCD which is composed of a plurality of CCD cells having sensitivities in the visible light region and the infra-red light region disposed in a matrix form.